In recent years, with the spread of the Internet, IT (Information Technology) has spread all over the world and revolutionized society. Particularly recently, an environment where the network can be accessed anytime and anywhere has been developed as is called a ubiquitous information society. In such an environment, individual identification systems attract attention, where ID (identification number) is assigned to each object so that the history thereof is revealed and utilized in production, management and the like. Specifically, RFID (Radio Frequency Identification) such as a wireless chip (also called an ID tag, an IC tag, an IC chip, a RF (Radio Frequency) tag, a wireless tag, and an electronic tag) is beginning to be introduced in companies, markets and the like on a trial basis.
In general, a wireless chip 100 is constituted by an antenna 101 and an IC chip 102 as shown in FIG. 8A. The antenna 101 and the IC chip 102 are often formed separately and then attached to be electrically connected to each other.
The IC chip 102 mainly includes a power supply generating means 103, a control means 104, a memory means 105, and a resonance capacitor portion 106 (FIG. 8B). The power supply generating means 103 rectifies and smoothes an AC signal received by an antenna, so that a DC voltage is generated. The power supply generating means 103 includes a capacitor called a storage capacitor portion 107 for holding charges after an AC signal is rectified and smoothed. The control means 104 extracts a data signal, a clock signal and the like from the AC signal received by the antenna, and transmits a modified AC signal from the antenna. The memory means 105 stores semiconductor device-specific ID data. The resonance capacitor portion 106 is provided in order that an AC signal with a predetermined frequency is received most effectively.
FIGS. 9A and 9B are schematic views of a capacitor 110. The capacitor 110 has a first electrode 111 and a second electrode 112 and the two electrodes are provided with an insulating film interposed therebetween (FIG. 9A). In a general capacitor, one electrode (e.g., the first electrode 111) is formed using a wiring or a semiconductor conductive film of an integrated circuit configuring a logic portion of a power supply generating means, a control means, a memory means or the like, while the other electrode (e.g., the second electrode 112) is formed using another wiring or semiconductor conductive film. The two electrodes are provided with an insulating film 113 interposed therebetween (FIG. 9B).